Water consumption from coal plants

Power generation has been estimated to be second only to agriculture in being the largest domestic user of water. To produce and burn the 1 billion tons of coal America uses each year, the mining and utility industries withdraw 55 trillion to 75 trillion gallons of water annually, according to the US Geological Survey.

It was estimated in January 2011 report by the Civil Society Institute, "Benefits of Beyond BAU: Human, Social, and Environmental Damages Avoided through the Retirement of the US Coal Fleet", that the number of gallons drawn per day for nuclear and coal power plants is 200 billion gallons. According to data collected by the United States Geological Survey (USGS), water withdrawals from thermoelectric power sources account for 49 percent of total withdrawals in the United States in 2005, or 201 billions a day.

Additionally, the debris from mountaintop removal is often pushed into streams, depleting freshwater supplies. Coal combustion produces the nation’s largest share of carbon dioxide and other greenhouse gases that are accelerating global climate change and also diminishing the nation’s freshwater reserves. And water is used daily in mining operations to cool and lubricate mining machinery, wash haul roads and truck wheels to reign in airborne particulates, and to suppress underground coal dust that otherwise could ignite.

Cooling
Water is used by thermoelectric generating facilities (coal, natural gas, and nuclear) to make electricity through converting the water into high-pressure steam to drive turbines. Once through this cycle, the steam is cooled and condensed back into water, with some technologies using water to cool the steam, increasing a plant's water usage. In coal plants, water is also used to clean and process the fuel itself. The U.S. Geological Survey estimates that thermoelectric plants withdrew 195 billion gallons of water per day in 2000, of which 136 billion gallons was fresh water. Researchers at Sandia National Laboratories put the estimate higher, finding that the typical 500-megawatt coal-fired utility burns 250 tons of coal per hour, using 12 million gallons of water an hour—300 million gallons a day—for cooling.

The two primary evaporative technologies for cooling power plants are categorized as wet and dry; hybrid systems are also in use. Wet systems dissipate heat to the atmosphere either by recirculating water through a cooling tower or by constantly replenishing an evaporative cooling pond. In the U.S. roughly 39% of coal plants use once-through cooling, while 60% evaporate heat via wet recirculating cooling towers or cooling ponds; less than 1% makes use of dry cooling, which use no water but are more expensive than wet systems. According to the Department of Defense National Energy Technology Laboratory (NETL), a wet recirculating cooling water system for a 520-MW coal-fired power plant uses about 12 million gallons of water per hour.

Processing and Cleaning
Although water requirements for cleaning or scrubbing coal are a fraction of those required for cooling purposes, they require a significant amount of water to produce and handle the various process streams, including limestone slurry and scrubber sludge. Makeup water requirements for a 550 MW coal-fired plant with a flue gas desulfurization island, to lower the emission levels for sulfur dioxide (SO2) under the Clean Air Act and help prevent acid rain, are about 570 gallons per minute (gpm), compared to about 9,500 gpm for cooling water makeup.

Burning
Power plants, like the Clinch River Plant, use tens of millions of gallons of water or more of freshwater daily. The coal turns the water to steam, the steam powers the turbines, and what’s left of the coal, the fly ash, is scraped from the smokestacks and stored in federally unregulated coal waste sites.

Mountaintop removal
Mountaintop removal (MTR) mining involves the blasting off the tops of mountains to reach the coal seams below, with the millions of tons of former mountains pushed into stream valleys. MTR has buried nearly 2,000 miles of Appalachian streams, while also contaminating drinking water, impairing water quality for river recreation, increasing water treatment costs for industry, displacing some communities, and increasing susceptibility to flooding for others.

Climate Change
Climate change from increased greenhouse gas emissions like carbon dioxide from coal plants is leading to decreased supplies of rain, snowmelt, and fresh water. Energy demand is increasing even as pressure steadily grows to limit greenhouse emissions and reduce water consumption.

Increased Water
Integrated Gasification Combined Cycle (IGCC), which converts coal into synthetic gas or syngas to extract more energy, is being promoted as a path toward carbon capture and storage; however as of 2009 capturing carbon dioxide (CO2) reduces plant efficiency and increases water usage. An Electric Power Research Institute study found CO2 capture equipment decreased plant output by at least 25% and increases water consumption by approximately 23%. Scientists with Sandia National Laboratories who’ve studied CCS say it will increase water withdrawal and use by 25 percent to 40 percent.

Contamination
Integrated Gasification Combined Cycle (IGCC) can also contribute to water contamination through cleaning the syngas. Coal gasification wastewater has an average pH of 9.8, while pure water has a pH of 7.0. The principal contaminant of “process wastewater” is nitrate, which contributes to algal blooms and dead zones. The Great Plains Coal Gasification plant in Beulah, North Dakota, generated 4.83 million metric tons of wastewater in 1988, contaminating local groundwater with high pH, sulfates, chlorine, arsenic, and selenium. The Department of Energy’s IGCC pilot project in Wabash River, Indiana, the Wabash River Generating Station, had selenium and cyanide limits that “routinely exceeded” legal limits.

Environmental Impacts from Coal Plant Water Usage
Heavy water usage from coal plants can have a long-term impact on aquifers in a region, since once depleted they can take hundreds of years to replenish. Power plants can also potentially harm fish eggs, larvae, and other aquatic biota in their early stages, as they require particular combinations of fresh water flow and temperature, among other factors, all of which can be impacted by coal plant water usage. Also, there can be thermal pollution from coal plants, as water not cooled to tolerable temperatures when released back into streams and rivers can kill fish populations or encourage excessive algal growth. Discharged water should therefore not only cleaned, but also cooled, requiring more water.

In addition to the threat of dwindling freshwater supplies, there is also considerable water pollution from coal, including negative health and environmental effects from the mining, processing, burning, and waste storage of coal, including acid mine drainage, thermal pollution from coal plants, acid rain, and contamination of groundwater, streams, rivers, and seas from heavy metals, mercury, and other toxins and pollutants found in coal ash, coal sludge, and coal waste.

In 2003, the Virginia Department of Environmental Quality drew attention to the acidity, sedimentation, and high concentration of heavy metals in its Dumps Creek, but didn’t name the source. But within Dumps Creek’s 20,000-acre watershed there are two active and two abandoned deep coal mines, and a mountain scraped off by mountaintop removal. Downstream, the Moss 3 Prep Plant pumps hundreds of gallons of water to process each ton of coal mined. Moss 3 separates the marketable coal from the minerals that will not burn by tossing in a chemical cocktail—the “trade secret”—a mix of coagulants and flocculants. Parts of the cocktail are benign, other parts are suspected to cause cancer and neurological disorders. Once the coal is washed, Moss 3 pumps the water-saturated waste—the coal slurry—back up the mountain into a dammed pond. Residents say existing water regulations - the Clean Water Act and the Surface Mining Control and Reclamation Act have been insufficient for protecting people from damaging effects.

Related SourceWatch articles

 * Climate impacts of coal plants
 * Mountaintop removal
 * Mercury and coal
 * Sulfur dioxide and coal
 * Global warming
 * Environmental impacts of coal
 * Thermal pollution from coal plants